Multipath Fading Channels Research Articles

SLM based Circular (6, 2) mapping scheme with improved SER performance for PAPR reduction in OCDM without side information

Abstract Like OFDM, OCDM signal also suffers from high PAPR. SLM is an attractive PAPR reduction method but it needs to transmit the information regarding phase sequence i.e. SI to the receiver, which results in reduction in SE and data rate. Various SLM based SI free and SI embedding schemes are available in the literature. In this paper, different possible quaternary to 8-QAM mapping schemes for SI free SLM based PAPR reduction in OCDM system are discussed. Moreover, a new mapping scheme to eliminate the SI requirement has also been presented in this manuscript for SLM based PAPR reduction in OCDM system. Proposed Circular (6, 2) mapping scheme doesn’t require SI at the receiving end which results in increase in SE and data rate as compared to standard SLM technique. Random sequence with phase factors {1, −1} is used to generate the phase sequences for the proposed mapping scheme. Also, the analytical expression for SER of Circular (6, 2) mapping scheme over AWGN channel is derived. We have also evaluated the mathematical expression for SER of other possible quaternary to 8-QAM mapping schemes. Computer simulation using MATLAB are also carried out to investigate the performance of all these mapping schemes in terms of PAPR reduction performance as well as SER performance over AWGN and multipath Rayleigh fading channel. Proposed scheme achieves the same PAPR reduction and improved SER performance w.r.t. other six schemes taken into consideration.

Joint Grouping Subcarrier and Permutation Index Modulations Based Differential Chaos Shift Keying System

A joint grouping subcarrier-permutation index modulation based differential chaos shift keying (GSPIM-DCSK) communication system is proposed in this paper in order to enhance the energy and spectral efficiency, and increase the data rate of grouping subcarrier index modulation in DCSK (GSIM-DCSK) system that was recently suggested. In this system, the reference chaotic sequence is loaded into a permutation generator block to construct different permuted replicas of the reference sequence, and the input data bits for each symbol duration are divided equally into G parallel groups, each group consisting of carrier index bits indicated by p1 used for selecting active or inactive subcarrier out of2p1 subcarriers for GSPIM-DCSKI and GSPIM-DCSKII systems respectively, and permutation index bits,p2, that are used to select one chaotic sequence out of 2p2 permuted replicas of the reference chaotic sequence and then used this sequence to spread the modulated bit,p3=1, to send it through active subcarriers so the total number of transmitted bits for GSPIM-DCSKI and GSPIM-DCSKII systems is G (p1+p2+ 1) and G (p1+(2p1-1)(p2 +1)) respectively. The expressions for energy and spectral efficiency, as well as the complexity of the suggested schemes, are determined and compared the outcomes with other traditional DCSK schemes. Under the influence of additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels, the analytical expressions for BER of the two proposed systems are derived. The simulated and analytical BER results are compared to confirm the precision of BER analysis. Additionally, a comparison is made between the findings of the proposed schemes and those of traditional DCSK schemes, indicating that the suggested methods boost the performance of traditional DCSK schemes.

Radio Frequency Fingerprint Identification With Hybrid Time-Varying Distortions

Radio frequency fingerprint identification (RFFI) is a promising physical layer security technique that employs the hardware-introduced features extracted from the received signals for device identification. In this paper, we consider an RFFI problem in the presence of hybrid time-varying distortions (HTVDs) induced by multipath fading channel, carrier frequency offset (CFO), and phase offset. To solve this problem, an HTVDs-robust RFFI framework is proposed. Firstly, we derive that the residual HTVDs after CFO correction can be approximated as multiplicative interference in the frequency domain. Secondly, we define a novel signal analysis dimension named spectral quotient (SQ) representation and then present the spectral circular shift division (SCSD) method to generate the HTVDs-robust SQ signals, where the multiplicative interference can be suppressed. Thereafter, the statistics including root mean square (RMS), variance (VAR), skewness (SKE), and kurtosis (KUR) are extracted from the real and imaginary components of the SQ signals, respectively. Finally, the statistical features are used for the training and testing of the support vector machine (SVM) classifiers. To further enhance the performance of the proposed RFFI scheme, we also present the spectral circular multi-shift division (SCMSD) method, which increases the flexibility in the generation of the HTVDs-robust SQ signals. Given what we knew, this is the first time attempting to mitigate the HTVDs by leveraging the strong frequency correlation at the neighboring subcarriers in the multivariate hypothesis tasks. Compared to several handcraft feature-based RFFI methods, the proposed method exhibits superior identification accuracy and strong robustness. Experimental results show that the proposed RFFI scheme can achieve the accuracy of 91.3%with five devices and 86.4% with sixteen devices when the classifiers are trained with the additive white Gaussian noise but are tested with the Rayleigh channel.

Design of Chaotic-Based PPM-PI-DCSK Modulation for Wireless Communications

In this letter, a joint pulse position modulation (PPM) and permutation index differential chaos shift keying (PI-DCSK) modulation scheme (PPM-PI-DCSK) is proposed to increase the data rate and improve performance. In PPM-PI-DCSK, the bit stream is divided into blocks of mp+mc+1 bits, where mp bits are modulated by PPM, mc bits are modulated by PI modulation, and the last one bit is modulated by DCSK. The theoretical bit error rate (BER) performance of the proposed PPM-PI-DCSK is derived over multipath Rayleigh fading channels and validated via simulations. Simulation results show that the proposed PPM-PI-DCSK outperforms the benchmark DCSK-based schemes. Furthermore, the performance superiority is also demonstrated by the frequency-modulated PPM-PI-DCSK over a typical ultra-wideband (UWB) channel. This demonstrates the superiority and feasibility of the proposed scheme in practical applications.

Performance of 5G NR-polar QAM-OFDM in nonlinear distortion plus Non-Gaussian noise over Rayleigh fading channel

The polar code readily provides rate adaptation, reaching Shannon’s capacity at low encoding and decoding complexity. It has entered the 5G New Radio (5G-NR) as a result of these alluring features to improve the bit error rate (BER) performance in Gaussian noise. In challenging environments for modern broadband communication systems, the amplitude and phase distortion caused by nonlinear distortion (NLD) of high-power amplifiers (HPAs), non-Gaussian noise or impulsive noise (IN), and multipath fading channels (H) play a significant role in BER degradation in an orthogonal frequency-division multiplexing (OFDM) system. Therefore, to improve the BER degradation of the conventional NR-polar QAM-OFDM system over such environments, different novel closed-form expressions of combined NLD-HPA and IN distributions and the log-likelihood ratios (Ls) at the OFDM demodulator output with and without Rayleigh fading channel have been derived. In addition, the novel derived closed-form BER expressions validate the derived distributions using Monte-Carlo simulation in the downlink (DL) and uplink (UL) scenarios. This system demonstrates a significant performance improvement and achieves a coding gain of 28 dB and 25.5 dB compared to the traditional coded OFDM system, which achieved only 10 dB in the case of IBO = 4 dB over the Rayleigh fading channel.

Performance of Broadcast Channel Using Hierarchical Modulation in OFDM Downlink

This paper proposes a multiple code block transmission scheme using hierarchical modulation (HM) for a broadcast channel in the orthogonal frequency division multiplexing downlink. We investigate the average bit error rate (BER) performance of two-layer HM using 16 quadrature amplitude modulation (QAM) and three-layer HM using 64QAM in multipath Rayleigh fading channels. In multiple code block transmission using HM, the basic information bits are demodulated and decoded to all users within a cell that satisfy the bit error rate (BER) requirement. Hence, we investigate non-uniform QAM constellations to find one that suppresses the loss in the average BER of the basic information bits for HM to a low level compared to that using the original constellation in which only the basic information bits are transmitted while simultaneously minimizing the loss in the average BER of the basic information bits for the secondary and tertiary information bits from the original constellations in which the information bits of the respective layers are transmitted alone. Based on the path loss equations in the Urban Macro and Rural Macro scenarios, we also investigate the maximum distance from a base station (BS) for the information bits of each layer to attain the required average received signal-to-noise power ratio that achieves the average BER of 10-3.

A New Receiver Design for Protograph-Coded Reference Reused DCSK Systems

In this letter, we investigate the performance of protograph-coded reference reused differential chaos shift keying (DCSK) systems to improve the transmission reliability. The traditional protograph-coded DCSK receiver does not take full advantage of the reused chaotic reference signals and hence cannot obtain desirable error performance. To solve this problem, we design a new receiver architecture called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">weighted reference estimation and iterative decoding (WRE-ID)</i> , which can universally improve the performance of protograph-coded reference reused DCSK systems over both multipath Rayleigh fading and additive white Gaussian noise channels. In particular, we put forward the WRE algorithm to estimate reference signal in order to calculate log-likelihood ratio (LLR) more precisely. Furthermore, extrinsic information output from the decoder is utilized to iteratively recalculate the weight of the WRE algorithm. As a further illustration, we derive the LLR expressions of the proposed WRE-ID-aided receiver of a typical protograph-coded reference reused DCSK (i.e., high-efficiency DCSK) system. Analytical and simulated results show that the proposed WRE-ID-aided receiver can always overtake the traditional receivers in reference reused DCSK systems. Hence, the protograph-based reference reused DCSK systems with the proposed receiver are very promising for high-rate high-reliability wireless applications.

Closed-Form Expressions of Upper Bound for Polarization-MDCSK System.

The performance analysis of polarization M-ary differential chaos shift keying (P-MDCSK) has been expressed using a tight upper bound with the Q-function. However, evaluating the Q-function directly is not a closed expression and there has been less work on closed expression for the upper bound. In order to solve the problem, this paper presents approximate closed-form expressions on the error probability of P-MDCSK. This expression is derived by employing a polynomial approximation of the Q-function. These closed-form expressions are verified through simulations conducted under both additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. The simulation results reveal that there exists only a negligible gap between the simulations and the derived closed-form expressions. For example, it is observed that the theoretical approximate closed-form expressions exhibit a marginal deviation of approximately 0.4 dB from the simulations when the bit error rate (BER) reaches 10-4. Although the proposed method can only give approximate closed-form expressions of the upper bound, it provides an effective method for other communication schemes where the exact BER closed-form formula cannot be obtained.

Performance Analysis of 5G New Radio LDPC over Different Multipath Fading Channel Models

The creation and developing of a wireless network communication that is fast, secure, dependable, and cost-effective enough to suit the needs of the modern world is a difficult undertaking. Channel coding schemes must be chosen carefully to ensure timely and error-free data transfer in a noisy and fading channel. To ensure that the data received matches the data transmitted, channel coding is an essential part of the communication system's architecture. NR LDPC (New Radio Low Density Parity Check) code has been recommended for the fifth-generation (5G) to achieve the need for more internet traffic capacity in mobile communications and to provide both high coding gain and low energy consumption. This research presents NR-LDPC for data transmission over two different multipath fading channel models, such as Nakagami-m and Rayleigh in AWGN. The BER performance of the NR-LDPC code using two kinds of rate-compatible base graphs has been examined for the QAM-OFDM (Quadrature Amplitude Modulation-Orthogonal Frequency Division Multiplexing) system and compared to the uncoded QAM-OFDM system. The BER performance obtained via Monte Carlo simulation demonstrates that the LDPC works efficiently with two different kinds of channel models: those that do not fade and those that fade and achieves significant BER improvements with high coding gain. It makes sense to use LDPC codes in 5G because they are more efficient for long data transmissions, and the key to a good code is an effective decoding algorithm. The results demonstrated a coding gain improvement of up to 15 dB at 10-3 BER.

On the BER Performance of Constant Envelope OFDM in Frequency Selective MIMO Channels With ML Detection

In this contribution, we investigate the issue of constant envelope orthogonal frequency-division multiplexing (CE-OFDM) transmission in multipath fading channels, by quantifying its bit-error rate (BER) performance with the aid of maximum likelihood (ML) detection in multiple-input multipleoutput (MIMO) configurations. Through theoretical derivation, we demonstrate the advantage of CE-OFDM over its traditional counterparts as original OFDM and discrete Fourier transformspread-OFDM (DFT-s-OFDM) in terms of BER performance, which is ultimately supported by the simulation results.

Pulse-Based ISAC: Data Recovery and Ranging Estimation for Multi-Path Fading Channels

Pulse-based integrated sensing and communication (ISAC) systems have the advantages of high ranging resolution and strong resistance to self-interference, compared with continuous wave (CW) based systems. However, for pulse-based ISAC systems, multi-path channels pose various challenges to data recovery and ranging by providing diversity gain for data recovery but incurring the interference to the identification of the first path in ranging. In this paper, we design a pulse-based ISAC receiver for multi-path channels. The designed receiver can obtain the diversity gain by correlating the received signal with the estimated template signal. Meanwhile, it can detect the arrival of the first path by using a threshold detection method based on a constant false alarm rate (CFAR). Furthermore, we extend the pulse-based ISAC design to a low-resolution analog-to-digital converter (ADC) scenario. A low-cost receiver design is provided for the pulse-based ISAC system that can recover data and estimate range simultaneously considering the non-linear effect caused by the low-resolution ADC. Simulation results show that compared with the generalized maximum likelihood (GML) based receiver, the proposed full-resolution pulse-based ISAC receiver has 1dB signal-to-noise ratio (SNR) loss in bit error rate (BER) and almost the same mean squared error (MSE) performance with the significantly reduced computational complexity. Also, compared with the full-resolution ISAC receiver, the ISAC receiver with 3-level quantization incurs only 0.8dB SNR loss in BER and 1dB SNR loss in MSE.

A Double-Threshold Channel Estimation Method Based on Adaptive Frame Statistics

Channel estimation is an important module to enhance the performance of orthogonal frequency division multiplexing (OFDM) systems. However, the presence of a large amount of noise in time-varying multipath fading channels significantly affects the channel estimation accuracy and thus the recovery quality of the received signals. Therefore, this paper proposes a double-threshold (DT) channel estimation method based on adaptive frame statistics (AFS). The method first adaptively determines the number of statistical frames based on the temporal correlation of the received signals, and preliminarily detects the channel structure by analyzing the distribution characteristics of multipath sampling points and noise sampling points during adjacent frames. Subsequently, a multi-frame averaging technique is used to expand the distinction between multipath and noise sampling points. Finally, the DT is designed to better recover the channel based on the preliminary detection results. Simulation results show that the proposed adaptive frame statistics-double-threshold (AFS-DT) channel estimation method is effective and has better performance compared with many existing channel estimation methods.

Performance Evaluation and Comparison Between LDPC and Turbo Coded MC-CDMA

This work presents a comparison between the Convolutional Encoding CE, Parallel Turbo code and Low density Parity Check (LDPC) coding schemes with a MultiUser Single Output MUSO Multi-Carrier Code Division Multiple Access (MC-CDMA) system over multipath fading channels. The decoding technique used in the simulation was iterative decoding since it gives maximum efficiency at higher iterations. Modulation schemes used is Quadrature Amplitude Modulation QAM. An 8 pilot carrier wereused to compensate channel effect with Least Square Estimation method. The channel model used is Long Term Evolution (LTE) channel with Technical Specification TS 25.101v2.10 and 5 MHz bandwidth bandwidth including the channels of indoor to outdoor/ pedestrian channel and Vehicular channel. The results showed that the performance of the proposed system was better when the LDPC was used as a coding technique

Concentric triangular mapping with iterative substitution method for PAPR reduction in OCDM system without SI

Abstract OCDM, a new MCM scheme, has been proposed in the literature. Like widely used OFDM, OCDM also has a drawback of high PAPR. PAPR reduction schemes like SLM and PTS require information about phase factors i.e. SI used at the transmitting end for PAPR reduction for recovery of original data signal at the receiver. Transmission and recovery of SI is always a concern. In this paper a new CTM-IS method has been proposed for PAPR reduction of OCDM signal without SI. Main objective of the proposed scheme is to improve the error performance of SI free SLM and PTS based schemes without any degradation in PAPR reduction. PAPR performance and SER performance, over AWGN as well as multipath Rayleigh fading channels, of OCDM signal with proposed CTM-IS scheme is evaluated. Analytical expression for SER of the proposed CTM-IS scheme over AWGN channel is also derived. The computational complexity of the proposed CTM-IS scheme is also presented. Performance of the proposed CTM-IS scheme is compared with the existing MSM combined with SLM (MSM-SLM), CCM combined with SLM (CCM-SLM) and OM combined with SLM (OM-SLM) schemes. The proposed CTM-IS scheme has demonstrated to offer a theoretical power gain of about 3.01 dB, 2.55 dB, and 14.23 dB over MSM-SLM, CCM-SLM and OM-SLM schemes, respectively. Proposed CTM-IS scheme provides better SER performance with respect to MSM-SLM, CCM-SLM and OM-SLM without any loss in the PAPR performance. Moreover, computational complexity of CTM-IS scheme is less than that of MSM-SLM and CCM-SLM schemes.

PERFORMANCE IMPROVEMENT OF TWO-WAY COOPERATIVE DCSK SYSTEM USING GROUPING SUBCARRIER-PERMUTATION INDEX MODULATION

This paper proposes a new two-way half-duplex cooperative communication system based on a new chaotic modulation scheme called Joint Grouping Subcarrier-Permutation Index Modulation-based Differential Chaos Shift Keying (GSPIM-DCSK) in order to enhance its energy efficiency, data rate, and BER-performance. GSPIM-DCSKI utilizes a permutation index to load additional data bits, and the input bits are divided into groups that contain carrier, permutation, and modulated bits. The active and within each group are selected based on carrier index bits. The energy and spectral efficiency of the GSPIM-DCSKI systems are evaluated and compared to GSIM-DCSKI. The performance of the new schemes is evaluated by calculating the bit error rate (BER) under different channel conditions. Finally, the BER performance of the new cooperative system using GSPIM-DCSKI is compared to a traditional cooperative system using DCSK and proves that the new cooperative system has a better performance than the traditional one in different channels. Simulation results show that at the multipath Rayleigh fading channel the proposed cooperative system gained SNR about 3 dB at a BER level of 10^(-3) at than the traditional one and this gain is increased to equal 4 Db when p2=4.

An Enhanced Channel Estimation for IEEE 802.15.4 OFDM Receiver in High-Speed Mobile IoT Communication Systems

Currently, orthogonal frequency division multiplexing (OFDM), standardized in IEEE 802.15.4, has attracted attention as a transmission scheme for higher data rates, long-distance transmissions, and mobile communications for the expansion of IoT applications as well as for legacy IoT applications, such as smart metering systems and home-area networks. In particular, receiving schemes using IEEE 802.15.4-based OFDM have been actively examined to realize mobile communication. Previous studies used the long training field (LTF) and pilot subcarriers for channel estimation of multipath fading, achieving mobile communication with data rates of 100 kbps or above at moving speeds of up to 40 km/h in an urban environment. In a previous study, channel estimates were obtained by repeating channel estimates from the LTF and pilot subcarriers in the time domain and by interpolating the estimates in the frequency domain. This study proposes a receiving scheme for IEEE 802.15.4 OFDM aimed at high-speed mobile IoT communication systems. In the time axis direction, the proposed scheme obtains channel estimates in the same manner as previous schemes. However, in the frequency axis, the proposed scheme obtains the channel estimates by copying estimates of neighboring subcarriers according to the coherence bandwidth of the multipath fading channel to update the channel estimates frequently. Computer simulation results show that the proposed scheme including delay spread estimation can achieve mobile communication with a data rate of 100 kbps at moving speed of 200 km/h in the urban environment.

Disentangled Representation Learning for RF Fingerprint Extraction Under Unknown Channel Statistics

Deep learning (DL) applied to a device’s radio-frequency fingerprint (RFF) has attracted significant attention in physical-layer authentication due to its extraordinary classification performance. Conventional DL-RFF techniques are trained by adopting maximum likelihood estimation (MLE). Although their discriminability has recently been extended to unknown devices in open-set scenarios, they still tend to overfit the channel statistics embedded in the training dataset. This restricts their practical applications as it is challenging to collect sufficient training data capturing the characteristics of all possible wireless channel environments. To address this challenge, we propose a DL framework of disentangled representation (DR) learning that first learns to factor the signals into a device-relevant component and a device-irrelevant component via adversarial learning. Then, it shuffles these two parts within a dataset for implicit data augmentation, which imposes a strong regularization on RFF extractor learning to avoid the possible overfitting of device-irrelevant channel statistics, without collecting additional data from unknown channels. Experiments validate that the proposed approach, referred to as DR-based RFF, outperforms conventional methods in terms of generalizability to unknown devices under unknown complicated propagation environments, e.g., dispersive multipath fading channels, even though all the training data are collected in a simple environment with dominated direct line-of-sight (LoS) propagation paths.

MODELING OF A DIGITAL COMMUNICATION SYSTEM WITH INTERFERENCE-RESISTANT CODING OVER DELAYED MULTIPATH CHANNELS FOR A FIXED WIRELESS ACCESS SYSTEM

&#x0D; &#x0D; &#x0D; In this study, an analysis of the performance of a digital communication system was conducted to improve the efficiency of the communication channel. The system was de- signed and evaluated in the MatLab/Simulink environment, specifically for the transmission of binary data in a multipath channel with static fading. One of the main advantages of this system is its ability to provide high noise immunity, even in the presence of noise, interference, and signal delays. The performance of the system was investigated in terms of bit error rate (BER) over both an additive white Gaussian noise (AWGN) channel and a multipath Rayleigh fading channel. The study also considered the impact of inter-symbol interference (ISI) and explored different parameters for a static channel, resembling a wireless LAN system based on IEEE 802.11 (as defined by Rec ITU-R M.1225). This study uses a solution to suppress inter-symbol interference using cascading coding (convolutional turbo codes with Reed Solo- mon code), Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT), amplifiers at the transmitter side and normalizer at the receiver side, by regulating the amplification ratios of transmitter and receiver sides. Modeling of a digital communication system for a wide-band fixed wireless LAN system (for Indoor office and Outdoor to indoor systems) has been performed. The modeling outcomes show that the applied method provides a good per- formance improvement in channels with ISI with static fading.&#x0D; The application of cascading coding (turbo code together with RS code), amplifiers, and FFT on the transmitter side, and IFFT on the receiver side will eliminate the effects of inter-symbol interference on digital signals in a multipath channel with static fading (as defined by Rec. ITU-R M.1225 for internal and external transmission systems) for wireless fixed systems.&#x0D; &#x0D; &#x0D;

Payload symbol-based nonlinear RF fingerprint for wireless QPSK-OFDM devices

Radio Frequency (RF) fingerprinting is one physical-layer authentication method for wireless communication, which uses the unique hardware characteristic of the transmitter to identify its true identity. To improve the performance of RF Fingerprint (RFF) based on preamble with fixed duration, a nonlinear RF fingerprinting method based on payload symbols is proposed for the wireless OFDM communication with the bit mapping scheme of QPSK. The wireless communication system is modeled as a Hammerstein system containing the nonlinear transmitter and multipath fading channel. A parameter separation technique based on orthogonal polynomial is presented for the estimation of the parameters of the Hammerstein system. The Hammerstein system parameter separation technique is firstly used to estimate the linear parameter with the training signal, which is used to compensate the adverse effect of the linear channel for the demodulation of the successive payload symbols. The demodulated payload symbols are further used to estimate the nonlinear coefficients of the transmitter with the Hammerstein system parameter separation technique again, which is used as the novel RFF for the authentication of the QPSK-OFDM device. Numerical simulations have verified the proposed method, which can also be extended to the OFDM signals with other bit mapping schemes.

Design and Analysis of a New Index-Modulation-Aided DCSK System With Frequency-and-Time Resources

We propose a new index-modulation-aided differential chaos shift keying (DCSK) system using frequency-and-time resources, referred to as CTIM-DCSK system, to achieve high-data-rate transmissions. In the proposed system, the orthogonal sinusoidal carriers are used to transmit both the reference-chaotic and the information-bearing signals. Moreover, the frequency-and-time resources are considered as indices to carry additional information bits. To simultaneously boost the bit error rate (BER) performance and reduce the system complexity, this paper proposes a new CTIM-DCSK signal based on the frequency-and-time resources, in which the time slots used by the selected subcarriers convey the same index bits. We employ a noise-reduction method at the receiver to further improve the BER performance of the proposed CTIM-DCSK system. We also derive the theoretical BER expressions of the CTIM-DCSK system over two different channels, i.e., additive white Gaussian noise (AWGN) channel and multipath Rayleigh fading channel. We analyze the data rate, complexity and spectral efficiency of the CTIM-DCSK system in comparison with the state-of-the-art counterparts. Analytical and simulation results verify the accuracy of the theoretical analysis and the advantage of the proposed CTIM-DCSK system. Consequently, the proposed CTIM-DCSK system appears to be a competitive candidate for low-complexity Internet-of-Things applications.